Amp Amps

leo stierer Bronze Member Username: Magfan USA Post Number: 79 Registered: Oct-07	Posted on Friday, January 04, 2008 - 06:17 GMT Why do amp manufacturers tout 'hi-current' as a benefit? My speakers have a 4amp tweeter fuse and cross over at 600hz. They are notoriously inefficient/low sensitivity so even if the woofer end can take say.....6amps, that is 10 amps total at maybe 70 volts. That would be 700watts at the absolute upper/ near destruction limit. A couple questions:: Why would I need an amp touting say.....35 amps? That appears to be 50% more than the speaker could tolerate. How fast is an AGC fuse? Can it take MORE than its rating and for how long? Isn't that the job of a Slo-Blo? PS, I just saw some 40$/each fuses today!!!
Eric Ramsey Silver Member Username: Eramsey South carolina United States Post Number: 578 Registered: Feb-05	Posted on Friday, January 04, 2008 - 08:07 GMT Leo slow down or your brain is gonna disentigrate. Granted a bat. as a source of power for a home audio amp has a promising potential but true 3P AC as in 3L from outlet in it's constant V glory would be for home audio: a) unecessary, b) expensive c) somewhat dangerous-some industrial 3P applications have no ground. d) overly complicated as homes would need switchgear-and much more wiring- very expensive. Nearly all home audio amps particulary those used in the US,Canada, and Mexico will have a max.speaker output V of about 30VAC rms. irregardless of stated slew rate or power supply V. http://www.audioholics.com/education/amplifier-technology/the-high-instantaneous -current-spec I would be shocked if you haven't read this. While I don't agree with everything these guys say, even though their math is certainly correct and they give in-depth informed reviews on mostly decent equipment, lets face it you can't assign numbers to perceived sound quality. http://www.grainger.com/Grainger/items/3XH85 Now that's a fuse my friends ER
leo stierer Bronze Member Username: Magfan USA Post Number: 80 Registered: Oct-07	Posted on Friday, January 04, 2008 - 17:36 GMT Eric, Thanks for the Audioholics article. NO, I hadn't seen it, or I'd have skipped my post. They finished the numbers I only started and showed how badly out of hand it can get, not to mention completely off-chart. The fuse I saw was not an industrial/giant unit. It was a std 32mm (1.25") fuse that goes in clips on a board or a 'fuseholder' In the industry I work in, which is a massive electricity user (6 digit monthly elec bill!!) we have a main plant breaker measured in cubic feet with a switch lever the size of a baseball bat! My brain cell exploded several years ago when I was up on top of a building during a lightning storm flying my kite. didn't hurt a bit!
Jan Vigne Platinum Member Username: Jan_b_vigne Dallas, TX Post Number: 11961 Registered: May-04	Posted on Friday, January 04, 2008 - 18:09 GMT . "From the math and what we know about the basics of how amplifier and loudspeakers perform we can now conclude that High Instantaneous Current is a non-issue and it has no application to driving contemporary and even most of the not so contemporary loudspeakers." Wow! I bet a lot of amplifier manufacturers would be surprised to read that. This is why I dislike Audioholics so much, they take a few select items to reach a predetermined conclusion. In this case, HT receivers don't do current, so don't worry about current. "My speakers have a 4amp tweeter fuse and cross over at 600hz." What speakers have tweeters with useable frequency response beneath 600 Hz? I'm not going to do the math but four Amps into a tweeter would be a phenomenal amount of wattage at 15kHz. This is what I would expect from a sound reinforcement system but not a home audio speaker. Consumer audio will normally have 0.75-1.5 Amp tweeter fuses and hope for the best with a tweeter crossed no lower than 2kHz. If these are your panels, Leo, then aren't we talking about a mid-tweeter with a fairly high current draw due to the inductive component of the quasi-ribbon driver. This is the frequency range where the Magnepans draw current which makes them somewhat unusual in the speaker world. Panels are about the only American made speaker with such high current draw at high frequencies, but they make up a significant portion of the "audiophile" speaker market. However, by the high frequency (tweeter) range, the amount of voltage is typically so low as to make high current less of a priority than when driving a Wilson or even a mid priced B&W where the largest capacitive component occurs within the low to mid band frequencies requiring the amplifier to work much harder. "Why would I need an amp touting say.....35 amps? That appears to be 50% more than the speaker could tolerate." You might also ask; why would anyone require a 1-2k watt amplifier? The answer would be; because you'll have the power when you want to use it. When you aren't using the power, you'll have a power supply operating in a broad relaxed comfort zone. If you're a fan of huge wattage, this suggests the sound quality will also be relaxed since the amplifier is essentially no more than a modulated power supply. If you're not a fan of huge wattage amplifiers, you say, "Hoowie!!! The power supply should be slightly larger than you'll ever require and no more is needed." I would say this is a case of both sides being correct and both overlooking some basic facts. High current came into vogue in the late 1960's when HK (primarily) began their research into the sound of amplifiers at the beginning of the age of transistor domination. Transistors offered the promise of high wattage and eventually high current delivery; something tubes don't do well or, most importantly, cheaply. While transistors measured "better" than vacuum tubes in many traditional respects, early transistors still left much to be desired in musicalality and sound quality when compared to the live event. HK began building broad bandwidth, high curernt amplifiers in an effort to correlate sound quality with measured performance. Experience had already shown that wideband frequency and power response had benefits which were broadly defined as "more natural" sound quality. With their early (output transformerless) solid state designs HK pushed those power bandwidth limits to 4-120kHz. This was quite a step away from the average amplifier of the day whose response was more closely aligned to the normal range of human hearing, 20-20kHz. HK emphasized square wave performance at all frequencies within the range of human hearing. To manage this sort of response, power supplies were developed which could slew sufficient voltage into a resistive load to maintain square wave accuracy at as high as 20kHz without overshoot or ringing. This required large power supply transformers and capacitors which gave the side benefit of high current availability into a typical loudspeaker load. At this point in time, I would say HK was not exactly pushing high current as a necessity for driving low impedance/high phase angle speakers since that sort of design wasn't common in the late 1960's. The high current capacity of the HK amplifiers was the result of the broad bandwidth design of the amplifier (with large power supply reserves) which gave excellent square wave performance. In a way, HK was divorcing the amplifier from driving a loudpseaker and merely looking at the amplifier as a single component. At the same time, the newest crop of acoustic suspension speakers and panels were demanding higher and higher amounts of wattage as the world of twenty five watt tube amps receded into the memory banks. With a fair amount of abandon the speaker designers would produce systems with extremely low efficiency and low impedance dips. (In 1975 I was selling the Acoustic Research 10pi with a nominal impedance of four Ohms and a nasty dip to about 2.8 Ohms, all at a spec'd 84dB sensitivity.) Crossovers became more complex with more power being absorbed by the crossover components (adding to the electricl phase component of the impedance) than in previous days of horn loaded systems with acoustic cut offs inherent in the design. Notch filters were introduced to compensate for the irregular frequency response of drivers of the day and cabinets with what we today consider to be archaic dimensions and antiquated cabinets. Altogether this created speakers that truly taxed most amplifiers power capabilites. As ER's linked article correctly suggests, this speaker concept reached its apex(?) in the late 1980's when models such as the large Infinity's and the Apogee panels dipped to 1.5 Ohms with a large inductive or capacitive component and then soared to as high as 64 Ohms. Obviously not a speaker for a "wimpy" amplifier. At the time power amplifier designers were trying to deal with simply remaining stable while driving these speakers in order to maintain what was, at the time, the "amplifier of the month" recommendation. Clearly, high current was the only thing that would drive these speakers, particularly at a time when no-negative feedback designs were also the rage. At about the same time Matti Otalla back at HK was introducing his concepts of amplifier performance which touted the reduction/removal of T.I.M. as a path to still more "natural" sound. Low T.I.M. specs depended heavily on faster power supplies to further broaden the power bandwidth of the amplifier. Simultaneously, on the other side of the US, Paul McGowan of PS Audio was designing a new pre amp, ostensibly the PS Audio 5.5. When he ran out of power transformers for his breadboarded design, he grabbed a transformer from a 100 watt power amplifier. The difference this bigger, stouter, stiffer transformer made in sound quality was evident and PS Audio began marketing this larger transformer as an after market upgrade to their pre amps. It wasn't long before large power supplies with massive transformers became the fad in high end audio appearing in everything from power amplifiers to cassette decks. All of this conspired to bring about the current trend in broad bandwidth, high current amplifiers needed to drive the insanely low impedance, high phase angle speakers we still see today. The amperage requirements of the average speaker will never exceed the amperage capability of most modern amplifiers at normal home audio volume levels. However, "average", "most" and "normal" are simply words that challenge some people. If your listening and buying habits are not "average" or "normal", you'll be someone who requires an amplifier with high current capability for those times when you severely stress the amplifier's power supply. Exceptionally "good" sound will require a power supply that handles not only the first drum thwack of the 1812 Overture but the entire cannon volley - at realistic levels. The instantaneous power required for each successive discharge will require a power supply with massive energy reserves since there is no time for the capacitors to recharge between shots. If the amplifier manufacturer is building for the most fanatical, worst case scenario (which it would appear many are), the amplifier will have high current capbility to survive and "sound good" throughout the worst moments without a sagging power supply dragging down performance. As I said at the beginning of this post, if this is the audio world you inhabit, you'll feel confident the amplifier is cruising along peacefully at all other times. The high current capacity of your typical 2007 amplifier was certainly meant for peak current delivery and not long term delivery. However, for the ocassional organ enthusiast who prefers sealed bass systems or the new generation of listeners who wish to replicate amplified, electrified rock concert levels through their home speakers, long term current delivery is important. More importantly, I would say, the capacity to deliver high current on a sustained basis is the goal. So the power supply in many amplifiers is built to deliver uninterrupted amperage into the most demanding loads. In the marketing driven world of high end consumer home audio, if you have the capacity, you advertise it. Apparently, from ER's linked article, in the HT world, if you don't have the capacity to deliver high current, you get someone to write an article saying it's not important. " somewhat dangerous-some industrial 3P applications have no ground" I never knew this. How is this done and what sort of hazard pay do you get for working on this stuff? .
leo stierer Bronze Member Username: Magfan USA Post Number: 81 Registered: Oct-07	Posted on Friday, January 04, 2008 - 20:32 GMT I tried to leave my panels out of it, so as not to slew the answers, since Magnepan is a semi-hot button issue with some.....They do not list a maximum, hard power limit but recommend a range. My old/sold MG-1s (original issue), had a 1.5 amp tweeter fuse and would suck my Cube absolutely dry. I think it was pretty much a dead heat which gave up first. I finally blew the fuse(S) and more than once to the point where I replaced them with 1.0A fuses as an additional layer of protection. I never blew these, having learned my lesson. sort of. So, with the Cube kicking out 200+/side and just being able to take out a 1.5amp fuse, I wondered about the juice needed to pop a 4 amp unit. I already know that speaker power limits are absolute rubbish and a speaker, except for the Ultra hi-efficiency Fostex/et al designs can take a huge peak of power without destruction. Except maybe for the 1812 you mentioned which should pin darn near any combo when cranked up. But if the amp rating of the fuse tracks with the power delivered, than I should be looking at near 700 watts before the fuse pops....clearly a nutty situation. As kind of an amp power supply aside, the Cube would make the lights in my house blink in time to the music! This tells me lots about how shoddy the house wiring is and the very low power storage capacity of the cube.....early tracking PS, and all. Another reason I asked was that the class 'D' stuff has me fascinated. Within a couple of weeks here, when the dealers receive some goodies, I'll go have a listen. A good integrated or the 3 piece BelCanto setup.....2 power amps and a pre run it in Biamp mode, will save me some valuable shelf space and not cook itself come summer. That will clear the decks for a real CD player and maybe the DAC-3, (dreamin on the last) Good answer.
Eric Ramsey Silver Member Username: Eramsey South carolina United States Post Number: 579 Registered: Feb-05	Posted on Wednesday, January 09, 2008 - 08:15 GMT Hello Jan and Leo, went out of town and been busy lately,you know how it goes. Just wanted to respond to a couple of points: My brain cell exploded several years ago when I was up on top of a building during a lightning storm flying my kite. didn't hurt a bit! I thank you Leo. I didn't mean to call you out- just joking around-thanks for being a good sport. You should be very careful with lightning it's extremely dangerous. In the industry I work in, which is a massive electricity user (6 digit monthly elec bill!!) we have a main plant breaker measured in cubic feet with a switch lever the size of a baseball bat! Yes in the plant I work in our power bill was 98 thousand dollars one month. And large industries using 3P power are usually given a discount! Our main in from Duke Power runs to a switchgear room with disconnect devices rated at over 400HP! From the math and what we know about the basics of how amplifier and loudspeakers perform we can now conclude that High Instantaneous Current is a non-issue and it has no application to driving contemporary and even most of the not so contemporary loudspeakers." High current capapbility in a ss amp is everything. That is certain. Look at the builds of powerful ss amps they all use very large transformers and often many large caps 10KuF or larger. The point that Audioholics makes that "instantaneous figures" are not really verifiable and unless a manufacturer is quoting this with a current measuring device connected to the ps while it is connected to a real speaker load, playing a source, not the obligatory non-inductive, 8 or 4 ohm resistor to simply get wattage figures then this spec is of little value. That is the part that I believe to be correct.Look no further than my profile and the many postings where I have discussed HK receivers and you will see I'm quite an HK fan. Other than prohibitively more expensive designs such as the Arcam and B&K, I believe them to be the best,dollar for dollar, on the market. The NAD's are also very good but to me their sound is more "flat" and neutral and not the sweet midrange of HK. The upper end Marantz are also solidly built with large scale devices in their power supplies as well. One of the best aspects of the way of HK builds amplifers, is their apparent refusal to use current limiting, which so many lesser brands of receivers do. As ER's linked article correctly suggests, this speaker concept reached its apex(?) in the late 1980's when models such as the large Infinity's and the Apogee panels dipped to 1.5 Ohms with a large inductive or capacitive component and then soared to as high as 64 Ohms. Obviously not a speaker for a "wimpy" amplifier. Wow! that must have made for a "train wreck" of a listening experience. somewhat dangerous-some industrial 3P applications have no ground" I never knew this. How is this done and what sort of hazard pay do you get for working on this stuff? My apology this does sound confusing,let me explain. Typically in many industrial plants, circuits that use 480V that remain below 1K amps do not have special ground fault systems as phase problem detection devices will provide limited control over ground problems. Also most DC subsystems have a "floating ground" in which the negative terminal is not directly grounded to the sub floor plant grid. This is done to ensure reliability as if a DC system has a polarization problem it will still operate and polarization problem detection devices will alert technicians to the problem so that it be corrected with little downtime. We have many DC motors used in our manufacturing process on our automated machinery. We will replace a subsystem transformer ocassionaly, although very rarely, I mentioned this on another thread. But we don't mess with the large Horsepower rated switchgear from the lines into our plant,we have contract electricians do this. The bulk of our work consists of new motor installations,or replacements and preventative maint. of motors, PLC programming and wiring changes in motor control panels. This is safe work as any decent electrician worth his salt with an ounce of training will completely de-energergize any equipment and follow lock-out and tag-out procedures as mandated by OSHA, before attempting any repair or maintanence work,so that he/she will not end up in the unemployment line or a funeral home. ER
Jan Vigne Platinum Member Username: Jan_b_vigne Dallas, TX Post Number: 12005 Registered: May-04	Posted on Wednesday, January 09, 2008 - 16:25 GMT . Floating ground I understand. Thanks.

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